Why I am getting error while using Pattern class to identify string whether its valid or not?

package app;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class ValidIdentifierDemo 

{

public static void main(String s[])

{

    Pattern p=new Pattern.compile("[a-z A-z][a-z A-Z 0-9]+"); //error here

    Matcher m=p.matcher("int");

    if(m.find()&&m.group().equals(s[0]))

    {

        System.out.println("Valid");

    }

    else

    {

        System.out.println("InValid");


    }

}

}